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Patel and Iversen published their first study on Snowball in 2008. (Irena Schulz was a co-author on the paper.) The following year, Adena Schachner, at the time a researcher at Harvard University, and her colleagues demonstrated that an African gray parrot named Alex—the Koko of the bird world, famous for his large vocabulary—could also move to a beat, as could Asian elephants and 13 other parrot species identified through an exhaustive search on YouTube. Further evidence came from Columbia University neuroscientist and musician David Sulzer, also known as Dave Soldier, who had been recording albums with an orchestra of Asian elephants in Thailand, for whom he had constructed supersized drums, gongs and chimes. Meanwhile, Yoshimasa Seki of the Brain Science Institute in Japan and his team successfully trained budgerigars (parakeets) to peck an LED in time to a wide range of tempos. In related experiments by other researchers, rhesus monkeys largely failed to learn rhythmic tapping tasks: They took more than a year to grasp the concept and even then were inconsistent and tended to lag behind the rhythm.
By 2012, the vocal learning hypothesis seemed to be transitioning from a tentative notion to a promising explanation of rhythm’s biological origins. Because people, parrots and elephants had all evolved to be vocal copycats, they had an innate talent for recognizing and replicating auditory rhythms; in contrast, acoustically inflexible primates did not. But then a single maverick mammal—one not known for musical prowess—leapt from sea to stage, stole the spotlight and urged the scientific community to reconsider.
A few years after word of Snowball got around, Cook, then a graduate student at the University of California, Santa Cruz, was contemplating a suitable research project for himself and Andrew Rouse, a UCSC undergrad. Cook was studying cognitive psychology, in particular the behavior of pinnipeds—walruses, seals, and sea lions—and he knew that Rouse had a passion for music. Perhaps, Cook thought, they could combine their interests and really put the vocal learning hypothesis to the test.
Though not quite as vocally proficient as parrots, walruses and seals can mimic novel sounds. In the 1970s and ’80s, one especially remarkable Atlantic harbor seal named Hoover learned to imitate human speech, greeting New England Aquarium visitors with phrases such as, “Hello there,” “How are ya?,” and “Get outta here,” all reproduced with a thick Kennedy-esque accent. Sea lions, however—separated from their pinniped cousins by more than 20 million years of divergent evolution—are not nearly as vocally flexible. “They can bark and grunt on command, at a fast or slow rate,” Cook said. “But they don’t seem to be able to alter frequency or produce novel calls.”
So Cook, Rouse, and their colleagues decided to try to teach a sea lion named Ronan to dance. At first, Cook trained Ronan to bob her head to simple metronome-like pulses of 80 and 120 beats per minute (bpm). But that did not prove Ronan had a general ability to identify a rhythm and move in sync; she might have learned to simply move at two specific speeds in response to two distinct sounds, the same way a dog might trot at one whistle and sprint at another. In a second experiment, Cook presented Ronan with beats she had never encountered before: 96, 88, 108, 132, and 72 bpm. This time she had to bob her head in time with the beats without any training or practice rounds. She performed superbly, sometimes slightly ahead of slower beats, or a smidge behind the faster ones.